Exergy flow diagrams as novel approach to discuss the efficiency of compressed air systems

Compressed air systems are among the major consumers of electrical energy in industry. As the importance of energy-efficiency grows in general, so does the need for valid and reliable metrics for discussing efficiency. Today, energy flow diagrams are a common tool to illustrate energy efficiency in compressed air systems. They are however subject to various shortcomings which are mainly related to their lack of transparency and reproducibility. Therefore, a novel approach for the assessment of efficiency is presented which is based on the exergy concept. This approach allows for a transparent calculation of flow diagrams for compressed air systems, including the possibility to illustrate the effects of a heat recovery system. The concept is illustrated at the example of an industrial set-up starting at the compressor inlet and ending at the application. The resulting diagram allows a more transparent and objective view on efficiency evaluations and thus contributes to a better understanding of energy-efficiency in compressed air systems and related applications.